The present invention relates to a processing system which reduces the number of poor quality workpieces resulting when the downstream production line to which the workpieces are delivered ceases demanding workpieces and movement of the workpieces through the processing system is accordingly temporarily stopped. More particularly, the present invention relates to a processing system having a multiple conveyor system for transporting workpieces through the system, in which processes already in progress are substantially completed even though portions of the conveyor system are stopped. The present invention is particularly suitable in systems for performing progressive processes--i.e., processes that proceed incrementally and thus should not be interrupted if completion is desired--including systems for coating coils or slots of components having a magnetic core, such as trickle impregnation systems. Such components include armatures and stators which are used in such electrical devices as motors and alternators.
Previously known trickle impregnation systems apply polymerized resins to wound coils of workpieces in order to bond together the wires. A protective coating of resin is also formed on the coil in order to protect against abrasion of the insulation coating present on the wires. The trickle impregnation system described herein or any other coil coating technique is particularly suited for treating components having a magnetic core such as wound armature coils or wound stator coils ("components").
Trickle impregnation is typically a four step process. First, the components are heated to a temperature which increases the viscosity of the impregnating resin when it comes into contact with the heated coil wire.
During the second step, which is the trickling operation, the components are exposed to trickle dispensers which drop liquid resin onto the heated coils so that the resin can run over the surface of the wires and also into the gaps between the wires. The impregnating operation should produce a component having wires completely coated by resin with the gaps between the wires totally filled, guaranteeing strong bonding.
After impregnation, the components are passed into a curing oven for a third processing step where the components remain for a predetermined time at a high temperature to harden the resin so that it reaches the required bonding and anti-abrasion characteristics. The hardened coating on the wire insulation satisfies the anti-abrasion requirement by preventing exposure to the abrasive atmosphere present in the final motor application.
In the final step, the components are exposed to a forced air flow which by convection cools the components in a required and sufficiently short time.
Typically, the components are transferred from one processing station to another by conveyors. After the impregnation process is completed, the components are transferred to a main production line conveyor in order to complete processing of the components prior to assembling them in the final motor. The conveyors of the processing stations are typically synchronized according to the intermittent demand schedule of the downstream main production line.
Satisfactory impregnation is typically guaranteed only when the entire system is functioning at regime conditions of the general production line. The above-described system presents a disadvantage when the downstream production line ceases demanding components, thereby stopping the conveyors during the impregnation process. Accordingly, components which are present and being treated in the trickle station can no longer advance for further resin application. If such stationary conditions last for more than a certain period of time, the partial amounts of resin which have been deposited on components in the trickle station begin to harden irreversibly. Any attempts to complete these components by adding further resin, which would otherwise cause the previously deposited resin to flow correctly to fill the gaps between the wires, usually are not successful after such irreversible hardening has begun. These components will be defective and are usually a total loss without the possibility of recovery.